1. Field of the Invention
The present invention relates to an optical fiber illuminator used for recording and reading high density optical information in a near field recording (NFR) scheme, a method of fabricating the optical fiber illuminator, an optical recording head, and an optical recording head and recording apparatus having the optical fiber illuminator.
2. Discussion of Related Art
In general, optical recording technology that uses focused laser light to record and read information onto/from an optical disk has been the focus of considerable attention as high capacity digital information storage technology.
In conventional technology using a lens optical system, a minimum spot diameter of an optical source is restricted to about half of a wavelength due to a diffraction limit, which limits recording density. Therefore, recently, a near field recording technology using an aperture probe has been widely used to overcome the diffraction limit.
The near field recording technology uses the principle that light passing through a hole (aperture) smaller than a wavelength of laser light propagates in an evanescent wave within a distance similar to the size of the hole. With an aperture probe positioned within a distance of one wavelength of laser light from a recording medium, marks smaller than a wavelength of the laser light can be recorded or read. Therefore, the near field recording device is capable of an extremely high storage density (200 to 400 Gbit/in2) compared to other existing optical recording devices.
Recently, as a near field recording technology using an aperture probe, technologies for recording and reading information at a high speed with the aperture probe formed on a cantilever or a planar slide head have been researched.
U.S. Pat. No. 5,517,280 (May 14, 1996) discloses technology in which a high-speed photolithography process having an optical resolution less than a wavelength is implemented with a number of cantilevers.
A number of cantilevers are caused to vibrate over photoresist, and radiate light through a protruding aperture probe. When the cantilevers vibrate upward and downward, a Van der Waals force is detected through a capacitive plate to control a gap between the aperture probe and the photoresist.
This method exposes photoresist through a number of aperture probes so that multiple nano-scale lithography processes can be performed. However, it is difficult to integrate an optical waveguide into the cantilever through a semiconductor process, and optical transmission efficiency from the optical waveguide into the aperture probe is low, making the method difficult to implement. In addition, the method lacks a specific driving and control technology for manufacturing a large-area scanner.
U.S. Pat. No. 6,466,537 (Oct. 1, 2002) discloses technology in which an aperture is formed on a planar head rather than a probe, and near field light emitted or absorbed from the aperture is measured to read information or control a gap between the head and the media.
The near field light emitted from the aperture is measured to control the gap, so that the gap can be controlled without contacting the probe. A gap between the head and the medium can also be controlled with a flying head used in hard disks. However, with a head arrangement having a signal aperture, this technology is readily adapted to a ROM arrangement for reading a recorded pattern, but it is difficult to adapt to an arrangement for recording information at a high rate.
Korean Patent No. 441,894 (Jul. 16, 2004) discloses a near field optical information recording and reading apparatus using a 1-D array type aperture probe and a micro integrated near field recording head.
Light emitted from an optical fiber comprising an optical illuminator is collected by a micro ball lens, diffracted by a micro mirror, and then incident on the aperture probe. Reflected light is detected with the optical illuminator to read recorded optical information.
However, with the above method, a process of adjusting the micro ball lens and the mirror to collect the incident light on the aperture probe is complicated. In addition, the reflected light is mixed with light scattered around the aperture probe so that it is very difficult to detect only the light reflected from the recording medium. Therefore, a method of reading information through measurement of transmission and so on should be further provided.
As described above, existing technology has many problems concerning an optical arrangement required in optical illumination and detection and a fast and stable optical connection. Consequently, there is an urgent need to improve the existing technology to facilitate its practical use.